Open link in background tab not always working

Every now and then when clicking a link with the middle button it does not open in a new background tab but in the active tab instead. I already noticed this behaviour in previous versions (at least 1.4 but probably 1.3 as well). It doesn't happen in any other browser so I suppose it is not hardware related. Another thing with respect to background tabs: Some of then, when fully loaded, pop to the foreground. This in my opinion is annoying.

This happens always when you click on link that is supposed to open the tab on background by default (that means you don't have to use middle click/ctrl+click). The only way how to go around this is by right-clicking and using "open link in new tab". The tab is absolutely empty - nothing in head and all you can see is blank page.
Fedora 24 64-bit with Gnome.
Vivaldi 1.5.609.8 (snapshot)
Attachments:

This happens always when you click on link that is supposed to open the tab on background by default (that means you don't have to use middle click/ctrl+click).

This might be the explanation but no solution as I don't know the programming behind the link and I don't want to know.
I only want Vivaldi to behave like Opera 12 (and every other browser I know) does:

Left click: Link opens the way the programmer meant to.

Middle click: Link opens in new background tab.
This is not because the other browsers work in this manner but because it is the easiest way for the user.